Automatic telephone system



`I-uly 30, 1957 F, KEssLER 2,301,285

AUTOMATIC TELEPHONE SYSTEM original med Jan.. $0; 195s s sheets-sheet 1 F I I mmvrole.

HTI-'ORNEY 4July 30, 1957 F. KEssLER 2,801,285

n 'AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 30, 1953 3 Sheets-Sheet 2 1Z0/PM i /NTERZ'LL TRU/VK C/RCU/T 200 INVMTOK H T TUR/VE Y July 30, 1957 F. KESSLER 2,801,285

AUTGMA'IIC TELEPHONE SYSTEM Original Filed Jan. 30, 1953' 3 Sheets-Sheet 5 AUTOMATIC TELEPHONE SYSTEM Frank Kessler, Los Angeles, Calif., assignor, by mesne assignments, to General Dynamics Corporation, a corporation of Delaware Original application January 30, 1953, Serial No. 334,197. Divided and this application January 7, 1954, Serial No. 409,473 t 9 Claims. (Cl. 179-27) This invention relates to electro-mechanical telephone systems and more particularly to means providing irn proved pulsing in an intertoll dial system. tion, which is a division of my copending application Serial No. 334,197, entitled Automatic Telephone System, filed January 30, 1953, may be used in conjunction with equipment shown in a co-pending application, Serial No. 308,240, iiled September 6, 1952, by Leon H. Reagan, now Patent 2,726,285, granted December 6, 1955, both this and the subject application having the same asslgnee.

Telephone equipment is arranged for both local and distant calls. In the past, distant calls have been handled by a procedure according to which an operator at a iirst exchange calls an operator at a second exchange: then This invenconnected with ground. For this reason, I refer to the negative poles as battery and the positive pole as grounded (-1-). It should be understood that this condition could be reversed or that any other well-known power source may be used without changing my inven-` tion.

Referring now to the drawings, only those portions which are germaine to the present invention will be de For a complete understanding of the entire system, of which the present invention is' scribed in detail herein.

part, reference should be made to my Patent 2,781,418, granted February 12, 1957.

Seizure The tirst call to be described is one in which an operator' OP100 receives a call in any conventional manner-such as by way of a plug and jack arrangement or automatic switch train, for example (neither of which is sh0Wn).

She learns that the call is for another oice which may be reached by way of a toll line such as TL103, for example. Therefore to forward this call, she tirst interconnects plug P101 and jack J 102 thereby seizing intertoll trunk circuit TC111. The other end of toll line` TL103 is signaled by any conventional means so that` toll line TL103 may be marked busy thereat, thus preventing the possible interconnection occasioned by two calls seizing the same trunk simultaneously from both ends. These operations may involve any suitable equipment at operator position OP100, such asthat shown omitted here, since it doesnot form part of the present invention, but is described in detail in my above-identified Patent 2,781,418.

Dialing rst digit The aforementioned incoming selector switch (not shown) is now prepared to receive switch. directing signals. Briey, the-operator at position 012100 proceeds to transmit digit signals in any suitable manner such as by pulsing over conductor M1 and dial leg DL110- to signal circuit TL122 where the signal pulses are repeated to conductor E for pulsing signal relay 140, thereby opening and closing contacts 141 to cause the. operation of. the incorningselector switch in amanner more fully described in my above-identifiedA Patent 2,781,418.v

More specifically, as relay 140 restores intermittently responsive to the incoming pulses on conductor E, slow release shunt relay 110 is'energized intermittently from grounded (-l-) ontcontacts 142, throughoperatedcontacts 218,v and the windingof shuntk relay 110 tol battery. Relayy 110operates and energizes a second shunt relay 230V overl a pathv which may be` traced from' grounded through operatedcontacts 116 and the winding of relay 230 to' battery. This relay operates to place amultiple marking on busy lamp L320' and on conductor Sof cable 700; Electrolytic capacitor C21-01s charged from grounded on contacts 116 through operated contacts 249A of` switchrelay 240; however, this device has no utility at this time; At contacts 112Y andk 113, shunt relay 110 opens the circuitV extending between toll line equipment TL121 and repeating coils RC111 and RC112`. Resistor R110 remains connected across the toll line by way of operated contacts 232 and 226 in parallel. This is to compensate for the removal of the repeating coil windings RC111 and RC112 while pulses are being-received, and to eliminate the momentary unbalancing effect of intermittent pulses on toll line equipmentisuch as TL1 11 and TL121, for example. In addition to the foregoing, shunt relay 110 also closes contacts 115toy connectv grounded from closed contacts 312 and 1-15 to'outgoing'conductor S1' in parallel with contacts 215. This is to hold succeeding equipment in an operated condition. The operation of relay 110 also connects variable resistor R120 across repeating coil windings RC111 and RC112 at operated contacts 114; however, this device has no utility at this time since it re-V la-tes to the correction of pulsing characteristics on outgoing calls.

Following the receipt of the rst 'pulse train, shunt relay 110l releases after its slow release time interval since contacts 142 remain open after the receipt of the last digitpulse.

Outgoing call from operator P314 over toll line T1103 Intertolll trunkcircuit'200 is adapted for outgoing calls destined for operator'OP100 as well as for the incoming call' explained above. To illustrate such a call, it is assumed that operator OP314 calls operator OP100 over plug CD311 to extend a call which was received in any suitable manner over plug CD313. lt is assumed that the equipment leading to plug CD313, cord circuit CD312 and operator circuit OP314 are all conventional equipment.

To extend this call, operator OP314 interconnects plug CD311 and jack 1310. Responsive thereto battery is connected from cord circuit CD312 through conductor 1313, andwindingv340A to grounded Sleeve relay 340v operates to light busy lamp L320 from grounded through contacts 341, and lamp L320to brattery, to guard this circuit against seizure by another operator. Relay 340 also connects grounded through contacts 343 to conductor S to guard this circuit against seizure by an incoming call from the aforementioned selector switch. energizes sleeve slave relay 120 Yfrom grounded In addition to the foregoing, relay 340 through normally closed contacts 247 and 323, operated contacts 342, through the winding of relay to battery. Upon operating, relay 120 locks through contacts 129E and 342. At contacts 122, relay 120 also opens the circuit extending ground to winding 260A. However, pulsing relay 260 operates from grounded through operated contacts 129B and 342, resistor R130, normally closed contacts 131, operated contacts 123, through winding 260A, normally closed contacts 243, operated contacts 129, normally closed contacts 245, and winding 260B to battery. Relay 260 operates and energizes release delay relay 270 from grounded through contacts 262, and the winding of relay 270 to battery.

A circuit is now closed for seizing equipment in the distant office over toll line TL103; This signal may light a lamp at operators board OP100 responsive to which she interconnects a suitable plug and jack; or this signal may seize an incoming selector over conductors S100, in which case dial pulses are necessary-to set telephone equipment at the distant office; For thel purpose ofexplaining this invention, it is assumed that an' incoming selector is seized.

The seizure signal results from operation ofl pulsing relay 260 which removes the groundmarking from the M lead at contacts 263; A circuit is then closed to connect battery through resistance lamp'L310, operated contacts 264, normally closed contacts 251 and 317 to the M lead. This marking operates equipment at the distant end. Also, the marking is used for subsequent pulsing and supervisory functions. Release delay relay 270 energizes direct ground relay 320 over the path from grounded through operated contacts 272, and winding 320A to battery. Relay 320 operates to connect a multiple ground through contacts 321 to busy lamp L320. Relay 320 also connects grounded from normally closed contacts 221, through operated contactsV 322 and 121 to low resistance winding 340B, and conductor 1313. The resistance of winding 340B is such that a supervisory lamp (not shown) lights in cord circuit CD312, which indicates to operator OP314 that she may transmit digit pulses indicative of the called number. Release delay relay 270 prepares a circuit, through contacts 276, to operate signal relay 220 responsive'to grounded markings on the E conductor as they may occur throughout the call.

To. prepare for dialing, operator OP314 connects battery tothe tip conductor of plug CD311 and jack .1310, through operated contacts 126, repeating coil Winding RC113, operated contacts` 127, winding A and grounded through operated contacts 124. Off-normal relay 130 operates over this path and in turn relay 130i closes a circuit to relay 360 extending` from grounded (not shown) applied from cord circuit CD312 by operator O P314 to the ring conductor of plug CD311 and then through contacts 129D, winding RC114, contacts 129B, 134, 352, 361 and winding 360A to battery. Relay 360 locks through x or preliminary operated contacts 363. The circuit to winding 350A is opened at contacts 362. When relay 130 operates it opens the path from grounded through operated contacts 129B, operated contacts 342resistor R130, contacts 131, 123, winding 260A, contacts 243, 129 and 245'to battery through winding 260B and grounded from the pulsing sourceV at operator. OP314, connected over the ring conductor of. plug CD 311 and jack .1310, is substituted therefore by way of contacts 129D, repeating coil winding RC114, operated contacts 129B, 134, 132, 123, through winding 260A, contacts 243, 129 and 245 to battery through winding 260B.

T oll4 line T L103 is Opened during pulsing; -Re1ay 260 is now adapted to respond to digit pulses successively dialed by operator. CD314. These digits will be repeated over the leadby an intermittent opening and closing of. pulsing contacts 264` to break the path extending from battery appliedthrough resistancelamp 1.310 and contacts 264, 251 and 317. As pulsing relay 260 restores responsive to each digit pulse, shunt relay 110 is operated from grounded (-1-) through contacts 261 and 273, to battery. When shunt relay 110 operates, it opens contacts 112 and 113 thereby breaking toll line TL103 during pulsing. However, the toll line remains terminated at all times because the equipment through which toll line TL103 is connected might become noisy if it were allowed to remain open; therefore it is terminated throughout this entire portion of the call by its characteristic impedance via the circuit which may be traced from conductor T through toll line equipment TL121, resistor R110, contacts 226, toll line equipment TL121 and conductor R.

Pulse compensation is provided while toll line TL103 is open. That is, pulsing relay 260 is connected to a source of dial pulses by way of the secondary winding of repeat coil RC111). If the primary winding of this coil were permitted to remain open, the characteristics of pulsing relay 260 would be changed and non-standard pulse ratios would result. More particularly,` pulses are transmitted over conductor M responsive to the operation of pulsing relay 260. Each time that contacts 263 close responsive to restoration of digit pulse relay 260, a digit pulse is transmitted over conductor M. Shunt relay 110 is operated simultaneously therewith when contacts 261 close. required for shunt relay 110 to operate; therefore, for the rst brief period of the lirst digit pulse the inductance of repeat coil RC110 is connected to toll line TL103. This inductance is removed by the operation of shunt relay 110 during the period that the first digit pulse is being produced. This would cause the rst digit pulse to have characteristics which are diierent from the ensuing digit pulses unless repeat coil RC110 presents the same characteristics throughout digit pulsing. To prevent this, shunt relay 110 closes contacts 114 to connect terminating retsistance R124) across secondary windings RC111 and RC112, thus returning the circuit to relay 260 to its normal condition. Following the last pulse in each digit pulse train, contacts 261 remain open and shunt relay 110 drops to return trunk TL103 to its normal condition.

Ofi-normal relay 130 releases after completion of the dialing procedure to restore the original holding circuit for pulsing relay 260. It will be recalled that ofi-normal relay 130 operated from battery applied to the tip of plug CD311 by operator OP314. She removes this battery at the end of dialing to break the path which formerly extended from that battery over contacts 126, repeat coil winding RC113, contacts 127 and winding 130A, to grounded at contacts 124. Pulsing relay 260 now holds from battery through winding 260B, contacts 245, 129, and 243, winding 260A, contacts 123, 131, resistor R130 to grounded through contacts 342 and 129B.

If the incoming selector at distant oice (not shown) is directively stepped to a level on which no idle trunk circuit is available, or stated otherwise, if overow is encountered, ground interrupted at the rate of 120 times per minute is connected to conductor E1 over dial leg DL110 and through operated contacts 276, to operate signal relay 220 at the rate of 120 I. P. M. This alternately lights and extinguishes a supervisory lamp (not shown) in cord circuit CD312. That is, contacts 221 open and close a path extending from grounded (-1-) through contacts 221, 322 and 121, low resistance winding 340B, the sleeve of jack 1310 and plug CD311, to a lamp (not shown) which will burn when in series with winding 340B but not when in series with winding 340A. It might be well to point out that contacts 322 closed when relay 320 operated. This was when pulsing relay A2160 closed contacts 262 to pull release delay relay 270 However, it should be noted that some time is which. irrtinn closed contacts 272 to operate relay 32o over an obvious circuit.

When thecalled lineis busy, a signal 1s returned 1n the form of an audible tone and ground pulses recurring at the rate of60 times per minute. This alternately lights: and extinguishes the supervisory lamp in thecord circuitA in the manner explained in the immediately preceding' paragraph except at halfthe rate, i. e., 60 I. P. M.

If the called line is not in use when seized, the called party hears a suitable. signal responsive to which he removes his receiver to operate relay 220 from ground o n conductor E and the supervisory lamp in cord circuit CD312 isextinguished accordingly. It is relighted when the receiver is replaced by the called party after comple- A tion of the conversation.

Upon receiving a supervisory signal Vat the end of the i conversation, operator OP314 takes-down the call by torelease relay 270. Contacts 272 are now open and.

so relay 320 drops.

False pulse Means is provided for reducing to a minimum the number of false pulses which may be transmitted. It may be recalled that digit and supervisory pulses are transmitted from intertoll trunk 200 to the distant oflice over conductor M by operation of contacts 263 and 264;

therefore, it is necessary to prevent false operation of pulsing relay 260 to avoid false pulsing on outgoing calls.

Since the operating path of pulsing relay 260 extends over two contacts (123 and 129A) on sleeve slave relay' 120, it is seen that only this slave relay need be controlled to avoid all such spurious pulsing. For example, if plug CD311 is quickly reinserted after having once been removed, relay does not immediately reoperate since release delay relay 270 and direct ground relay 320 must fully restore before sleeve slave relay 120 can reoperate over the path extending from grounded through contacts 323, i. e., from contacts 129B through contacts 323 and 342 to battery through relay 120. This precautionary feature is provided to prevent a momentary restoration of pulsing relay 260 and a resultant Ifalse pulse. If plug CD311 originally is inserted in such a manner that conductor .1313 is momentarily opened to restore sleeve relay 340, sleeve slave relay 120 will not restore-provided the momentary restoration of relay 340 is not of greater time duration than the slow release characteristic of relay 1Z0-again avoiding a false pulse. However, if relay 120 does, responsive to the momentary restoration of relay 340, relay 120 will not reoperate until after relays 270 and 320 fully restore.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modiiications may be made without departing from my invention in its broader aspects. I therefore aim to cover in the appended claims all such changes and modiiications as fall within the true spirit and scope of my invention.

What I claim is:

1. In an automatic telephone system, a iirst exchange comprising an operator position and an outgoing trunk circuit, a distant oiiice, a plurality of talking conductors for interconnecting said distant oflice and said outgoing trunk circuit, means at said operator position for transmitting switch directing signals over said trunk to said distant exchange, means in said outgoing trunk circuit for opening said talking conductors during signal transmission and means for terminating each side of said talking conductors in their characteristic impedance while open.

2. An automatic telephone system comprising an operator position, an outgoing trunk circuit, a distant oflice,

antoll lineinterconnectingsaid distantofce and saidoutf going trunk circuit, means in said outgoingA trunk circuit.

for, transmitting ashpsupervisionover said. toll'r line, means in said outgoing, trunk t circuit for opening said toll line during saidfiash supervision and means for. terminatingeach, sideof said. open. toll'. line in its characteristic impedance whi1e:open.

3. In'anautomatic telephone, systern a rstexchange,

said auxiliary ,conductor to said. distant-.oce, means. atv said rst exchange for opening said talking. conductorstransmitting means` comprises a: relayconnected to said second windings.

5. A. pulse correcting trunk circuit comprising incorn-y ing and outgoing talking conductors, a repeat coil for inductively connecting said'incoming' and outgoing talking conductors, means for transmitting digit pulses into said. trunk` circuit over said, incoming talking conductors, means responsive to said incoming digit pulses for transmitting4 outgoing digity pulses, means responsive to the irstdigit. pulse in each. incoming pulse train for disconnectingsaid repeat coil@ from said outgoing talking conductors, and means' simultaneously operative therewith for terminatingsaid repeat coil insimulation of saidy outgoing talking, conductors.

6L The trunkci'rcuitroffclaim 5 andvmeans for. terminating said outgoing conductors during thev time that said repeat coil' is ldisconnected.

7. Arpulse correcting trunk circuit comprising incoming and' outgoingtalking` conductors, a repeat coil for interconnecting said incoming and outgoing'talking conductors, means for transmitting digit pulses over said incoming conductors to said trunk circuit, means responsive to said incoming digit pulses -for transmitting outgoingy pulses from said'trunk circuit, means responsive to thel lirst digit pulse for openingV said outgoing conductors thereby to prevent the transmission of digit pulses over said outgoing, conductors; andl means effective simultaneously with the-openingof saidV outgoing conductors for maintaining a characteristic impedance across said incoming conductors whereby said digit pulses all have similar characteristics.

y8; The trunk circuitof claim 7 wherein said last named'means comprises, a resistor connected in series withthat portion of the repeat coil which formerly was connected with said outgoingtalking conductors.

9. The' pulse correcting trunk` circuit of claim 8 and meansY for terminating said outgoing trunk conductors with their. characteristic impedance.l

References Cited in the tile of this patent UNITEDy STATES PATENTS 

